The present invention relates to a navigation system for a vehicle having stored route or road data which, in response to entry of a destination, is searched to determine an optimum route of travel and to provide guidance information to a driver of the vehicle as the vehicle travels along the optimum route.
Various types of navigation systems have been proposed in the prior art to enable smooth driving of a vehicle along a route unfamiliar to the driver. In response to input of a destination, guidance for travel along an optimum route is provided during travel along the route. Such prior art systems have fixed road data, such as intersection data, node data, map data, etc., stored in a CD-ROM which is searched to determine the shortest route from the present position to the destination. The driver is often given the opportunity to modify the determined route by selecting an alternative road from a displayed map. The searched route is displayed on a screen and voice directions may be given to provide guidance.
In these conventional route guidance systems, the road data recorded in the CD-ROM is generally limited to main roads such as roads having a minimum width. Minor roads or roads which are narrower than the minimum width are not included and thus not available for searching and route guidance.
Additionally, there may be an alternative road preferred by a driver because of familiarity, favorable traffic conditions or other reasons. This alternative road has road data in the CD-ROM but is not selected by the guidance system search because of system search preferences. Modifying the searched route to substitute this alternative road in the guidance route requires additional effort by the driver and additional delay because of the need to re-search at least a portion of the route.
It is an object of the present invention to enable user addition of road data of roads not included within the recorded fixed road data.
It is another object of the present invention to provide system searching which takes into account user road preferences.